The invention relates to an arrangement for controlling the feeding of bars in bar loading magazines for automatically feeding bar material to machine tools.
Federal Republic of Germany patent DT-PS No. 1,777,170, and corresponding U.S. Pat. No. 3,131,587, teach the positioning of a bar by means of a control chain. The control chain, upon engagement of a start switch located in the path of the bar feed, by means of a controllable coupling is frictionally engaged and is stopped after the traversing of a measured distance corresponding to the spacing between the start switch and the cut-off tool of an automatic screw machine, when a cam on the control chain engages a stationary stop. The feed chain, frictionally engaged with the control chain, is then likewise arrested, and in that way effects the positioning of a new bar for feeding.
The aforedescribed arrangement, in which the distance-measuring means senses the proper positioning of the bar in terms of the engagement of fixed stops by moving cams, is not suitable for some applications, for example continual feed of a length of bar corresponding to the workpiece length without a fixed stop in the machine tool. Furthermore, in the aforedescribed arrangement, bar retractions subsequent to each workpiece feed, which might be necessary when the bar loading magazine is working together with a turntable indexing machine to give free space for rotational movement of the clamping arrangement on the turntable, are impossible to perform.